javascript-obfuscator · sanex3339 · Jun 10, 2026 · May 31, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,9 @@
 Change Log
 
+v5.4.4
+---
+* Fixed `Invalid regular expression` error when obfuscating code that uses ES2025 RegExp pattern modifiers (e.g. `/(?i:abc)/`). Fixes https://github.com/javascript-obfuscator/javascript-obfuscator/issues/1410
+
 v5.4.3
 ---
 * Fixed `controlFlowFlattening` occasionally dropping the `?.` short-circuit on `foo?.(arg)` calls, causing `TypeError: <X> is not a function`. Fixes https://github.com/javascript-obfuscator/javascript-obfuscator/issues/1408

diff --git a/package.json b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "javascript-obfuscator",
-  "version": "5.4.3",
+  "version": "5.4.4",
   "description": "JavaScript obfuscator",
   "keywords": [
     "obfuscator",

diff --git a/src/constants/EcmaVersion.ts b/src/constants/EcmaVersion.ts
@@ -1,3 +1,3 @@
 import * as acorn from 'acorn';
 
-export const ecmaVersion = <acorn.Options['ecmaVersion'] & number>13;
+export const ecmaVersion = <acorn.Options['ecmaVersion'] & number>2026;
diff --git a/test/functional-tests/issues/issue1410.spec.ts b/test/functional-tests/issues/issue1410.spec.ts
@@ -0,0 +1,46 @@
+import { assert } from 'chai';
+import { NO_ADDITIONAL_NODES_PRESET } from '../../../src/options/presets/NoCustomNodes';
+import { JavaScriptObfuscator } from '../../../src/JavaScriptObfuscatorFacade';
+
+//
+// https://github.com/javascript-obfuscator/javascript-obfuscator/issues/1410
+//
+describe('Issue #1410', () => {
+    describe('ES2025 RegExp pattern modifiers should be parsed without errors', () => {
+        describe('inline case-insensitive modifier `(?i:...)`', () => {
+            let obfuscatedCode: string;
+
+            before(() => {
+                const code: string = `console.log(/(?i:abc)/.test('ABC'));`;
+
+                obfuscatedCode = JavaScriptObfuscator.obfuscate(code, {
+                    ...NO_ADDITIONAL_NODES_PRESET
+                }).getObfuscatedCode();
+            });
+
+            it('should not throw an `Invalid regular expression` error and should preserve the regex literal', () => {
+                assert.match(obfuscatedCode, /\/\(\?i:abc\)\//);
+            });
+
+            it('should produce semantically equivalent code', () => {
+                assert.isTrue(eval(`/(?i:abc)/.test('ABC')`));
+            });
+        });
+
+        describe('disabled modifier `(?-i:...)` within a case-insensitive regex', () => {
+            let obfuscatedCode: string;
+
+            before(() => {
+                const code: string = `console.log(/(?-i:abc)/i.test('ABC'));`;
+
+                obfuscatedCode = JavaScriptObfuscator.obfuscate(code, {
+                    ...NO_ADDITIONAL_NODES_PRESET
+                }).getObfuscatedCode();
+            });
+
+            it('should not throw an `Invalid regular expression` error and should preserve the regex literal', () => {
+                assert.match(obfuscatedCode, /\/\(\?-i:abc\)\/i/);
+            });
+        });
+    });
+});